So I've been using Skritter for about six months at this point, and I find that I'm starting to lose some of the characters I learned months ago much faster than Skritter is making me review them. Not to the level at which I can't read them--that's not an issue. But I'm starting to confuse different radicals on the older characters to the extent that I couldn't write them in the wild. I've looked through all the settings and I've bumped up my target retention rate and I've followed the FAQs and I grade myself very strictly using the grading buttons, but I don't feel I can really write 97% of the characters I have learned at any given time. I'd say I can write perhaps 85% and read most all of them.

Does anyone have any suggestions as to how I can review older characters more effectively without having to manually go through and study sections I think I might be lacking? What do you do in this sort of situation?

Grade them more harshly when they come up - be much stricter about assigning "so so" grades if you needed any hints or had any hesitation in writing them and that should do it (over time).

What icebear said, but be stricter with 'so so' grades to the extend of avoiding them completely for items with long review dates. If you don't know the character, tell Skritter that you don't know it. If something comes up every 6 months, and you tell Skritter you know it 'so so', it'll be another 5 months or so until you next see it, but you'd see it in 5 days or so if you selected 'don't know'.

Consider "starring" the words (click on small star in upper right corner" to put them into a special list you can then study in a concentrated manner. I recommend nputting no more than 30 in at a time before "drilling" them into your memory.

The starring idea is a good one, but I'm still beyond strict with myself in terms of grading, so I don't know what else there is to do. I feel that the characters I'm forgetting are just not coming up for review so I can't grade myself down on them or star them!

Setting a higher retention target percentage would help in the long run, wouldn't it ?

I think not adding new words for a while, will also work. You will get more 'older words' than before.

红羽, one thing you could do is this:

1) Export all your words, characters only
2) Put them into a spreadsheet
3) Delete the writing column
4) Randomize the order
5) Print it out
6) See how many you can actually write from memory

If you have been being very strict with yourself, then I would be surprised if the score you get is much different than the ~91% character writing retention rate you've been hitting lately. If it is, let me know what characters you missed and I can look at what's going on with the scheduling for some of them and see what we might improve.

When did you change your target retention rate to 97%? That setting does take a long time to have its full effect.

I think that shooting for really high retention rates usually leads to a ton of reviews, at a high cost to overall learning speed.